1. Field of the Invention
This invention relates to new and useful 5-substituted picolinic acids and salts thereof, 5-substituted picolinic esters and 5-substituted picolinic acid amides, to a process for preparing the same, and to pharmaceutical compositions containing the same.
2. Description of the Prior Art
It is known that hypertension often includes apoplexy, heart trouble, etc., which necessitates extensive research for new and useful anti-hypertensives.
Fusaric acid (5-n-butylpicolinic acid) is known to be useful as an anti-hypertensive agent as disclosed in Jap. J. Pharmacol., Vol. 25, 188 (1975), however, fusaric acid has a butyl group at the 5-position of the picolinic acid moiety and has a low LD.sub.50 value. As a result, an improved anti-hypertensive agent is desired.
British Pat. No. 1,502,055 discloses that 3-substituted-2(1H)-pyridone-6-carboxylic acid can be used as an anti-hypertensive agent but the anti-hypertensive activity (i.e., maximum depression in blood pressure) thereof is poor and an improvement is desired.
The inventors have already synthesized 5-alkoxypicolinic acids and evaluated them as anti-hypertensive agents as reported in Japanese Patent Application No. 116641/1976 (corresponding to U.S. patent application Ser. No. 838,180, filed on Sept. 30, 1977). It has now been found that the compounds of the present invention exhibit anti-hypertensive activity equal or superior to 5-alkoxypicolinic acids of the Japanese patent application No. 116641/1976 and have lower toxicity than 5-alkoxypicolinic acids of the Japanese Patent Application No. 116641/1976 and, therefore, the compounds of the present invention are useful compounds for the treatment of hypertension.